Wind-tunnel research comparing lateral control devices particularly at high angles of attack 13: auxiliary airfoils used as external ailerons Page: 3 of 32
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AUXILIARY AIRFOILS USED AS EXTERNAL AILERONS
indicated on figure 2 was sufficient to eliminate any
noticeable interference effects on the wing.
When the ailerons were mounted so as to remain
at a fixed angle relative to the main wing, the counter-
weight shaft was replaced by a screw (see fig. 3) and
locking screws clamped the locking quadrants (fig. 2)
to the supporting brackets. The angular interval
between holes in the quadrant was 50.
Wind tunnel.-All the present tests were made in
the N. A. C. A. 7- by 10-foot open-jet wind tunnel.
In this tunnel the model is supported in such a manner
that the forces and the moments about the quarter-
chord point of the midsection of the model are meas-
ured directly in coefficient form. For autorotation
tests the standard force-test tripod is replaced by a
special mounting that permits the model to rotateAll measurements of forces and moments on the
wing model were obtained from the 6-component
balance in the form of the absolute coefficients (lift,
CL; drag, CD; rolling moment, C'; yawing moment,
C,'; and pitching moment about the quarter-chord
point, C 44'). The coefficients in all cases were based
upon the total wing area and were not corrected for
tunnel-wall effect. The center-of-pressure location is
given in percentage of the main wing chord.
The investigation covered 48 positions for the aile-
ron axis as given in table II. In general, the tests at
each position were divided into four main subdivi-
sions, as discussed in the following paragraphs. The
extent to which the tests were carried out in detail
depended upon the importance of the position in
question.FIGURU 3.-Wing model with external ailerons mounted in posItion .
about the longitudinal wind axis passing through the
midspan quarter-chord point. This apparatus is
mounted on the balance, and rolling-moment coeffi-
cients can be read directly during forced-rotation tests.
A complete description of the above-mentioned equip-
ment is given in reference 4.
TESTS AND RESULTS
The tests were conducted in accordance with the
standard procedure and at the dynamic pressure and
Reynolds Number employed throughout the entire
series of investigations on lateral control (reference 1).
The dynamic pressure was 16.37 pounds per square
foot, corresponding to an air speed of 80 miles per
hour at standard density; and the Reynolds Number,
based on the chord of the main wing, was approxi-
mately 609,000.(1) Preliminary tests.-Preliminary force tests were
made at each aileron position to determine the best
angular settings of the ailerons (when neutral) for
maximum lift and minimum drag. From the results
of these tests neutral angles were chosen for the sub-
sequent tests and the most favorable method of using
the ailerons as an aid to the general performance char-
acteristics of the main wing was decided upon. Thus,
the ailerons in all the positions shown in group A were
found to be most efficient when held fixed at an opti-
mum angle at which were obtainable the best values
of both CL_ and CD,.,,. Similarly, in group B best
performance was attained by using the ailerons as
flaps. In group C the maximum value of the lift co-
efficient and the minimum value of the drag coefficient
were best obtainable by allowing the ailerons to float81
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Weick, Fred E. & Noyes, Richard W. Wind-tunnel research comparing lateral control devices particularly at high angles of attack 13: auxiliary airfoils used as external ailerons, report, July 23, 1934; (https://digital.library.unt.edu/ark:/67531/metadc66166/m1/3/: accessed May 9, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.